Thirty-five-year-old Schaffhausen has pleaded guilty to three counts of first-degree intentional homicide, but he maintains he is not responsible for the killings of 11-year-old Amara, 8-year-old Sophie, and 5-year-old Cecilia because of a mental illness. The St. Croix County District Court trial is to determine his sanity.

Meloy is expected to be the final witness for the defense. He is attempting to prove that Schaffhausen was in a "dissociative state" at the time of the crimes.

When asked if Schaffhausen suffered from a mental disease or defect, Meloy said yes. "He lacked substantial capacity to conform his conduct to the requirements of the law," Meloy said.

But the prosecution argued that Schaffhausen was able to conform his conduct to the requirements of the law up until the day of the murders.

Meloy performed two evaluations and several tests on Schaffhausen. One of the tests is the Minnesota Multiphasic Personality Inventory (MMPI), which is one of the most frequently used personality tests in mental health.

The test indicted that Schaffhausen felt "unjustly blamed for other people's problems," Meloy said. Schaffhausen also felt that he got a "raw deal" out of life.

But people with this kind of profile don't all commit murder, Meloy said, and people with the profile are not all insane. Meloy also said most people who are depressed do not kill people.

When asked if testing took malingering into account, Meloy said there was no indication of Schaffhausen faking responses on his tests.

Meloy said Schaffhausen has a personality disorder that affects interactions with other people in a "destructive way" but that he's not psychopathic or antisocial. "[Schaffhausen] doesn't view other people as whole, real, meaningful individuals," he said.

Later during questioning from the prosecution, Meloy said that Schaffhausen showed some antisocial conduct by violating the law.

Schaffhausen has a drunken-driving conviction. He reportedly stole from his employer by falsifying timecards, and he choked his roommate, Meloy said. At the time, he did not lack the capacity to understand right from wrong.

Meloy testified Schaffhausen "would cry easily, was volatile, angry, would threaten, and he was obsessed with [his ex-wife] Jessica Schaffhausen .... This is a complicated individual.”

He said Aaron Schaffhausen didn't have a close relationship with his father; he was rejected by his dad and grew dependent on his mother and then dependent on Jessica Schaffhausen as a result.

He also said antidepressants were to blame for Aaron Schaffhausen's increasingly erratic behavior in the spring of 2011 and that drinking exacerbated his depressive state. Jessica Schaffhausen testified Aaron Schaffhausen was taking Celexa, which is used to treat depression, at one point.

'Catathymic Homicide'

Meloy called the case a "catathymic homicide," which is usually associated with a dependent personality and leads to an "explosively violent act that is out of character for the person" and then "relief."

He said the fact that Aaron Schaffhausen changed the girls' clothes and put them in their beds is the heart of catathymia, a "gross and dangerous contradiction in his mind, that on the one hand he can be homicidal and slaughter his daughters, and within moments of that he can be tucking them into bed and kissing them."

Catathymia is the existence of unconscious material so emotionally charged or affect-laden that conscious effects are produced. "In catathymia, the only option becomes, 'I either kill myself or I kill others, or I do both,'" Meloy said.

Aaron Schaffhausen reportedly told Meloy that he didn't have any thoughts or feelings when he was killing the girls. Meloy explained that when the feelings are intense enough, Aaron Schaffhausen could "dissociate" as if he was observing himself; there was intense emotion, he just wasn't consciously feeling it.

Meloy testified that he didn't receive all the evidence in the case because of "budget limitations on his time." But he was aware of the lack of evidence when he wrote his report in March 2013, Meloy said.

Differing Medical Evaluations

Meloy has a much different analysis of Aaron Schaffhausen's mental state than the court-appointed medical expert, Dr. Ralph Baker, who testified Monday. Baker said he believes Aaron Schaffhausen is depressed and possibly obsessive compulsive but that he is not insane. He also told the jury about Aaron Schaffhausen's own account of what happened the day of the murders.

According to Baker, Aaron Schaffhausen said, "It was a spur-of-the-moment thing." Baker said he looked "very depressed and sad and tearful" during that moment.

Aaron Schaffhausen reportedly told Baker he gave the girls money for their piggy banks and talked to them about his plan to drive them down to the river on the day of the murders. Cecilia couldn't find her shoes, so Aaron Schaffhausen told Baker he was helping her look for them. The next thing he knew, he said he was strangling her until he thought she was dead.

When Aaron Schaffhausen went down to the kitchen, Amara and Sophie reportedly came back inside and he heard Cecilia crying, so he knew she wasn't dead. Sophie was attempting to take care of Cecilia when Aaron Schaffhausen allegedly got a knife and cut the three girls' throats.

He reportedly told Baker he planned to light the house on fire but decided not to do it.

"He's seen what he is no longer a part of, that he is there in the home and emotionally, he is no longer a part of this family, a part of the girls' lives," Meloy said in his testimony Tuesday. "I think that there was a grief and a sadness and a rage that began to occur in him at that time."

A number of Aaron Schaffhausen's family members were in the courtroom Tuesday, including his parents. On Monday his parents testified Aaron Schaffhausen struggled with mental illness his entire life.